Like it or not, there is something about cocaine that excites the imagination. Not so much its chemical effect, which invariably leads to blabbering self-absorption, but more its social legend.

Whereas other drugs enjoy fleeting periods of fashion, cocaine has managed for many decades to retain a glamour and fascination way beyond its mundane reality. Perhaps this is because it's usually consumed via a large-denomination bank note or maybe it's the historical jet-set associations, but the abiding image of cocaine is decadence in powder form. The moment a banker snorts coke in a television drama, for example, we understand that he is damned, an over-stimulated symbol of western venality and excess. And this vision of club-class dissolution is only enhanced by the knowledge that in developing countries, peasants scrape a living, gangsters risk death and drug barons make a killing out of cocaine.

In many ways, the story of the drug from coca leaf in Bolivia to mirror in Belgravia is the story of our modern-day anxieties and preoccupations: globalisation, exploitation, crime, violence, government control and consumer power. A multibillion-dollar industry, the business of cocaine is nothing to be sniffed at.

There is a great book to be written that draws all these various aspects of the trade together into a powerful narrative about the global market. That Tom Feiling's The Candy Machine: How Cocaine Took Over the World is not that book is a disappointment, compounded by its ambition to be the "story of cocaine as it's never been told before".

Feiling starts well, by sketching the origins of the trade. Coca wine, a combination of red wine and cocaine, was popular in the United States in the 19th century. Abraham Lincoln bought a bottle of Cocoaine just a month before he was elected president. By the turn of the century, cocaine cost 25 cents a gram and was used in a variety of pharmacological remedies, including a cure for childhood shyness. Most famously, cocaine was the active ingredient in Coca-Cola until 1914. The soft drink, minus the alcohol, evolved from Peruvian wine cola. The company's red and white livery, we learn, was taken from the Peruvian flag.

This is all entertaining information, but where the book starts to go astray is in allowing a polemic against prohibition to inform not just its argument but its tone. A hectoring voice intrudes on almost every page, attacking the futility and hypocrisy of the west's and, in particular, America's stance on drugs, while all but celebrating the ingenuity and derring-do of the cocaine cartels.

As it happens, I think that Feiling is largely correct, in that prohibition and the so-called "war on drugs" have created more problems than they have solved. One of the book's many sobering statistics is that there were 200,000 Americans in jail in the early 1970s, when the war on drugs began in earnest, and there are now 1.8 million, with another 5 million on probation or parole. Half a million of those imprisoned are there on drugs-related charges. And a strikingly disproportionate number are black and poor.

A similar pattern, albeit on a much smaller scale, has taken shape in Britain over the same period. Anyone looking at the problems that beset the inner cities needs to ask if the global policy on drugs has worked. After all, as Feiling points out, if we can't keep drugs out of our prisons, what chance is there of preventing them from getting on to the streets?

Still, it's also worth asking if prohibition is preventing a bad situation from getting worse. At best, Feiling pays lip service to this argument, preferring instead to see the whole issue of anti-drug initiatives and law enforcement as a sort of conspiracy of stupidity. This often causes him to lose perspective. He argues, for example, that taking cocaine while pregnant may increase the risk of low birth weight, but is not associated with particular birth defects; by contrast, heavy drinking "during pregnancy causes foetal alcohol syndrome, but nobody wanted to hear about the dangers of drinking while pregnant". Really? Nobody? Except perhaps a whole generation of mothers.

Feiling has put in a good deal of research, both in the library and, more impressively, on the ground, in Colombia, Mexico, Jamaica and the States. However, his travels don't form much of a picture on the page. Feiling's background is in film documentary, a medium where description is largely surplus to requirements. The video image of the location creates the atmosphere, conveys the milieu. But in print, a sense of place and person has to be worked at and it is something that has been neglected here.

The drug dealers, drug users and law enforcement officers that Feiling interviews come across as material to support an argument rather than fully formed people with lives outside the narrow frame of the author's reference. In his eagerness to present us with the global "Candy Machine", he fails to animate the people who man it. The result is that far from demystifying the cocaine trade, Feiling reinforces the idea of two self-contained worlds – the traffickers and the law enforcers – locked in an abstract battle for supremacy.

He is to be praised for producing an appraisal of drug policy that seeks to be more realistic, but in doing so he loses sight of actual reality, that rich accumulation of situations and detail that ensnares the casual reader.